import sys

n=int(input())
w=[int(i) for i in input().split()]

def dfs(index,right,left):

    if index==n:
        if right == left:
            print("possible")
            sys.exit()
        return

    dfs(index+1,right+w[index],left)
    dfs(index+1,right,left+w[index])

dfs(1,w[0],0)
dfs(1,0,w[0])

print("impossible")